This invention relates to the heating of various grains, nuts or seeds by microwave energy and has particular reference to appliances for making popcorn of the like within a microwave oven.
It is commonly known that heat may be applied to grains, nuts seeds or kernels for various purposes. Edible nuts may be roasted, rice grains may be puffed and popcorn kernels may be popped by application of heat either radiatively or convectively in well known conventional ovens fueled by electrical energy, by the burning of liquid or gaseous fuel or by combustion of solid fuel.
Popcorn has been made in many ways. Kernels have been placed in a screenlike container with a long handle so that the container may be held suspended above an open flame. Since the heat from the flame usually radiates onto or contacts only one side of the supply of kernels, it was necessary to vigorously shake the container so that all the kernels would be heated and to prevent burning of the popped corn. Another method was to place a supply of kernels in a covered pan disposed on a burner of a kitchen range, for example, and again shake the pan to properly heat all the kernels and to agitate the popped corn. Still another method has been to place the kernels in an enclosure having wall areas containing electrical heating elements. This method again usually requires that the enclosure be at least slightly agitated. In all of these methods, butter and salt must be subsequently added.
In a copending application Ser. No. 865,824, filed Dec. 30, 1977, and assigned to the same assignee as the present invention there is disclosed an appliance for heating nuts, seeds, kernels and the like by microwave energy and which comprises a substantially conical bowl which holds the kernels in its lower end and which has a large interior volume above the kernels to allow the popped kernels to rise in the bowl when heated. However, microwave energy usually is distributed through substantially the entire oven cavity and attempts are generally made to control the energy so that it is distributed substantially uniformly throughout the oven. Popping of corn in such an appliance takes a relatively long time even when the kernels are clumped in the bottom of the bowl.